1. Field of the Invention
The present invention relates to methods for manufacturing decorative workpieces such as decorative panels.
2. Description of the Related Art
Gravure, offset and flexography are being increasingly replaced for different applications by industrial inkjet printing systems, which have now proven their flexibility in use, such as variable data printing making short production runs and personalized products possible, and their enhanced reliability, allowing incorporation into production lines.
Inkjet technology, as digital printing technology has also caught the attention of manufacturers of decorative surfaces, such as laminate floor. In the current production process for manufacturing decorative panels as shown by FIG. 1, a paper manufacturer (11) supplies a paper roll (12) to a decor printer (13) who uses gravure printing (14) in order to deliver a decor paper roll (16) to a warehouse (17) of a floor laminate manufacturer (20). Some decor printers (13) are now investigating inkjet printing (15) instead of gravure printing. Rotogravure printing on the porous decor paper generally uses ink having a viscosity at 25° C. of 1 to 2 Pa·s, while the viscosity of inkjet inks is much lower, often about 1 to 15 mPa·s at 25° C. The floor laminate manufacturer (20) stores the decor paper rolls (16) having different decorative patterns in his warehouse (17). Depending on the market demand, the floor laminate manufacturer (20) then selects the decor rolls (16) with the desired decorative pattern in his warehouse (17). The selected decor rolls (16) are then impregnated (18) and cut to size (19) for manufacturing ready-to-use floor laminate (21). The warehouse (17) is necessary as a buffer for sudden large market demands of a specific floor laminate because there is a large time delay between ordering and delivering of new decorative paper rolls (16).
An approach to reduce the size of the warehouse and time delays is treated by EP 2431190 A (THEODOR HYMMEN), which discloses in FIG. 1 a method for producing a digitally printed sheet, web or plate-shaped workpiece (20) with wear-resistant surface including the steps of: A) providing a digital data set to a digital printing device (1); B) providing a printable workpiece (20) to the printing apparatus (1); C) digital printing at least an acrylate printing ink (22) on the printable workpiece (20) using the printing apparatus (1) and thereafter supplying a resin mixture (5, 21) to the digitally printed workpiece; and D) curing the resin mixture (5, 21) by means of a heated press (7). The time delay can be avoided by the floor laminate manufacturer incorporating the manufacturing of decorative paper rolls into its own production process.
Also aqueous inkjet inks have been used for manufacturing decorative laminates by single pass inkjet printing. For example, in the Palis roll-to-roll single pass printing systems (http://www.palis-digital.com/en/portfolio/sp-drucker.html) aqueous inkjet inks are printed on a paper substrate having a special ink acceptance layer.
To manufacture a decorative workpiece, comprising a decoration layer which carries a digital printed decorative pattern, the finishing of the decorative workpiece such as cutting and/or adding a tongue-and-groove profile is not accurate. In the state-of-the-art the decorative pattern printed on the decoration layer is a large selection from a decorative image which shall be finished to a decorative workpiece. But due to inaccuracies in the finishing (for example cutting), it is not known which part of the decorative pattern remains comprised in the decorative workpiece.
EP2556962 (HUELSTA WERKE HUELS KG) discloses a bleed area in FIG. 1 with reference number 8 as peripheral edge but the bleed area is an unprinted area or contains extra information, like a barcode which is also disclosed in FIG. 4 with reference 11.
EP2695746 (UNILIN BVBA), which became public available on 12 Feb. 2014, with a date of filing on 6 Aug. 2012, discloses a method wherein multiple rectangular-shaped decorative patterns are printed on a decoration layer. In paragraph [0011] they disclose a method to allow for tolerance while cutting by selecting a larger region of interest in a decorative image. But in a digital print workflow the decorative image is often not known by the manufacturer of decorative workpieces so selecting a larger region of interest from the decorative image is not possible.
Another way to allow tolerances is by enlarging the decorative pattern, but this manipulates the outlook of the selected region of interest from a decorative image which should be avoided.